The objectives of this project are to determine whether or not the mouse mammary tumor virus (MuMTV) requires association with genetic or carcinogenic factors in order to effect cell transformation. This is approached by the experimental infection in vitro of permissive cells with various MuMTVs produced in tissue culture by established mammary tumor lines. Following exposure to sublethal doses of radiation or carcinogens either prior or after infection to MuMTV, the cells are monitored by membrane immunofluorescence (MIF) for virus replication, by cell aggregation viability assay (CAV) for transformation and transplanted in vivo to confirm their tumorigenicity. Other objectives are to assess the diagnostic value of antigens extracted from mouse mammary cell lines by the leukocyte migration inhibition assay (LMI). Comparative assays are to be done with antigens extracted from human breast tumor cell lines of various sources: scirrhous carcinomas, infiltrating ductal carcinomas, metastatic pleural effusions and solid metastasis. In this case the migratory response of peripheral leukocytes collected from normal and breast cancer patients will be evaluated.